Diverse patterns of El Niño–Southern Oscillation impact on the carbon balance of North American ecoregions
Wu Sun, Carnegie Institution for Science, wsun@carnegiescience.edu (Presenter)
Kelsey T Foster, Stanford University/Carnegie Institution for Science, ktfoster@stanford.edu
Yoichi Paolo Shiga, NASA Ames Research Center / USRA, yoichishiga@gmail.com
Nina Alessandra Randazzo, Environmental Defense Fund, nrandazzo@edf.org
Julian Merder, Carnegie Institution for Science, jmerder@carnegiescience.edu
Anna M Michalak, Carnegie Institution for Science, michalak@carnegiescience.edu
The El Niño–Southern Oscillation (ENSO) is the leading mode of internal variability in the climate system and impacts the carbon balance of North American biomes. Assessing ENSO impacts on the carbon cycle is key to understanding ecosystem sensitivity to climate, informing the mechanisms driving interannual variability in regional carbon balance, and predicting how carbon fluxes respond to changing ENSO variability and intensity in future climates. While El Niño boosts North American carbon uptake, impacts on specific North American ecoregions and the underlying mechanisms are less clear.
To address this gap, we use top-down estimates of North American land carbon uptake, derived from in situ atmospheric CO2 observations and remotely sensed solar-induced chlorophyll fluorescence patterns, to examine the sensitivity of North American carbon uptake to ENSO at the ecoregion scale.
We identify ecoregions in which net carbon uptake is most sensitive to ENSO variability. During El Niño, we infer increased net carbon uptake in the Pacific Northwest, subtropical drylands, and Central Gulf Coast. Conversely, El Niño suppresses summertime carbon uptake over the Upper Midwest. ENSO impact on the seasonal patterns of carbon uptake varies among ecoregions, with the most pronounced impact occurring in spring for the Pacific Northwest and in summer for other mid-latitude ENSO-sensitive ecoregions. We further show that ENSO impacts on carbon uptake are mainly mediated by moisture-related anomalies such as in vapor pressure deficit and precipitation, but some ecoregions are additionally affected by anomalies in temperature and radiation. Our findings show that identifying ecoregion-specific responses to ENSO is essential for advancing the predictive understanding of interannual variability of carbon uptake.
Associated Project(s):
Poster Location ID: 1-38
Presentation Type: Poster
Session: Poster Session 1
Session Date: Tue (May 9) 5:00-7:00 PM
CCE Program: TE